underwater diver rigging winches with swivel base

[roymack]

hello,

does anyone know of a good company that could help in sourcing underwater diver rigging winches with swivel base? these are to be used to adjust spool positioning on the seabed. i have had one quote from the company, All Oceans, based in the uk, but they were pretty expensive. has anyone got any recommendations?

thanks

 

[JLSeagull]

Try Cal Dive International c/o

http://www.helixesg.com/contactinformation.html

 

[Ussuri]

If you are just taking about manhandling a spool on the seabed whats wrong with dropping down a DMA and rigging off that with a Tirfor winch?

 

[doig]

Roymack, pardner you need to share a LOT more information to get this job well understood. What are you trying to do? And where are you? (GOM? Indonesia?) What resources are available or are you determining that? Hopefully you are. Are there any platforms at the site and associated w/ this effort (floating? fixed)? Is this a riser tie-in? Or,a P/L tee tie-in.? What is the water depth? Visibility? P/L spool length? Offsets? Diameter? Weight while being handled? How joined to P/L (Misalignment flanges? FIxed weld-neck flanges, one side Swivel-ring flange)?. These are minimum questions to know and to pass on.

You are keen to use a bottom founded, diver-operated swivel bottom(?) winch. Why? Is this the answer and the only solution? I would be surprised if it is. FYI, in general, it it far easier for a diver to rig snatch blocks UW and tie-back to anchors, jacket legs, etc, and to run the live end to the surface and fairled to a fixed winch, capstan etc. Yes, there has to be radio contact and very careful coordination w/ the surface winch operator and diver or ROV on the bottom. You can also have the controls in the diver's hands but that complicates things. In any event a winch (wherever it is, on bottom of on a deck) needs to be restrained to a reaction point and needs power provided to it from somewhere. Power is generally surface supplied (hydraulic power, compressed air, water, or electric power). Since all of these need to be surface supplied, the running end can be taken to the surface and taken to a surface winch on the platform or boat (existing capstan, windlass or winch). Seems far smoother to me that way.

MOST of all draw up 2-D and 3-D sketche (plan and elevation)and THINK it through. Its really elementary physics. Make a scale table-top model w/ cord and mini-blocks to demonstrate to divers or ROV operators what you are trying to do and how you want it done. Be ready to change your mind as they will have better ideas and likely have done it before. Use their ideas and give them credit for them. Once the drawings are as you want them, give them to a good structural ACad designer and let him make a saleable presentation that you can e-mail around for comments. Agaim: Accept the good comments, jettison the bad ones. Keep asking yourself: "What do I need to do to cause this (or that) action to occur, given the resources I have? What other resources or changes in the ones I have are needed to 'get there'). Remember, this is very simple physics, but it has to work! Keep it safe, keep it simple, make it work! Show it and be able to demonstrate what you want!)

Best suggestion I can offer: Sit down early in the planning phase w/ your sketches w/an old GOM diver and ask him to review and offer suggestions. That's all these guys do: underwater rigging. It's as natural to them as breathing or drinking a cold beer after a long decompression. Ask a second diver, but separately: Ask them together, you'll just get a fight. There are several ways to skin these cats. Again, pick the best, leave the rest.

Ask and ye shall receive. Knock and it will be opened unto you.

Let us know how you make out or get the details to us as outlined above, maybe one of us can help (Most of all find that old GOM diver!).

Good luck. Sorry this got so long-winded, but you have to know these things.


Ima-Nemisis Doig
(an old diver)

 

[roymack]

guys,

thanks very much for the info there.

JLseagull...thanks for the name, i have sent them an email to see if they could help.

Ussuri...yeh, thats basically what i'm hoping to do is to attatch a swivel winch onto a DMA. i'm trying to contact companies that could supply an appropriate winch, then its a case of designing a bolt connecting it to the DMA

doig...thanks for that info, i'll use those suggestions during the planning stage.

we are just needing a mechanical aid for alligning the spools. i am based in scotland with the work being carried out in the north sea. there is a riser on one side of the pipeline that is being replaced with the otherside just being a Tie-In-Point (tip) to another pipe. the water depth is 75m & we're dealing with a 24" pipeline being used for oil. the spools have taper-loc flanges.

we were also thinking that we could attach a bracket onto the spools that need moving together & attach the winches to the brackets, so that the winches were sitting ontop of the actual spools, then threading the winch wire through the bolt eyes on the two flanges then simply winching the two spools together.

has anybody done this kind of work before & can suggest if this could work or suggest a better method for manhandling spools on the seabed.

thanks

 

[doig]

Roymack, returned from Scotland about a month ago in the Stirling and Thornhill area, ancestral home area of the Doigs. Great place.

1. What is your role here? Operator-engineer, a contractor working w/ the Operator? Or, are you w/ a diving contractor putting this this spool in? All of these are as if you are working with the Operator or as an engineering company working for the operator.

2. Riser: What if the distance between the face of the jacket and the TIP? At 24" it's probably a gas line, correct?

2. Is there an expansion of other offset to square the flanges up between the riser and TIP? Or is the spool a fairly straight shot that can be made up w/mis-alignment taper-loc (T-L) flanges?

3. The riser is being replaced? How? With a DB? or brought out on a barge/boat and rigged into place w/ come-alongs (tifors) and chainfalls into pre-set clamps?

4. When is the riser being installed?

5. What is the DMA acronym? Seems like a bottom-founded alignment frame? If so, that's right on. Aquatic of Scotland used to have a series of these frames with hydraulic lifts and shifts. Do you have a diving group involved yet? to repeat, this is their bread and butter.
Or, do you want to develop "the" solution and simply tender "it" to be done and provide all of the "tools" to do it? Generally it's more practical to define what you want, in place, provide the basics (Coated pipe lengths and fittings for the spool, T-Ls, swivel flanges, bolts, nuts, etc as free-issue material) and let get a tender package out to several qualified dive companies to both propose their solutions and provide a quote. Their SOW might include: making final spool measurements, have the spool made up, NDE and hydrotest, install and final test. Usually, the best solution will surface from the returned tenders and will be the least costly which is what you want, isn't it?.

I can't see what the diver operated swivel-base winch will do for you. If the diver group who will be doing the work would need it, they'll either get it (rent it) or fabricate a base for a static winch.

good luck,

Ima-Nemisis Doig
(an old diver)

 

[Ussuri]

DMA = Dead Man Anchor

 

[Ussuri]

Are air bags an alternative?

 

[roymack]

doig....i am an engineer for a "surface - seabed" oil & gas service company, so our client is an operator. the actual riser is not being replaced, we are replacing a 12km section of pipe & as such have spools at each end to tie into (a) the spool that connects to the riser at one end and (b) the existing pipeline. it is a 24" oil pipeline. as ussuri said...DMA is indeed a dead man anchor, otherwise known as a clump weight. we actually carry out the diving operations aswell from our dive support vessels, a meeting has been organised with the offshore crew to put some ideas together. as ussuri has previosly mentioned, it is possible to do the job by rigging of the DMA using a tirfor winch. the only problem with this is that the DMA has to be positioned very accurately in line with the spools, therefore having to use more diver time, hence why we are trying to develop a swivel base for the winch so that the DMA can be placed without accuracy & the swivel will correct any rotation needed, therefore saving time & money. so a design 4a swivel has to be carried out if we are to go ahead with the swivel base idea, otherwise we will have to go ahead with the rigging off the DMA.

has anyone got any thoughts on what would be more appropriate for the situation. any ideas would be welcome.

oh yeh, scotland is a great place, i am scottish myself....its just a shame about the weather here though!

cheers

Roy

 

[roymack]

ussuri...yeh we are going to be using airbags as an aid aswell. as i mentioned the swivel base idea is to save diver time, so we'r just trying to see if its a feesible plan for the project or whether the costs involved with the swivel will outweigh the benefits. if thats the case the good old rigging off the DMA with a tirfor would be the option that we would use.

cheers for the input.

 

[Ussuri]

Roymack

While not knowing your exact field layout I would think that even using a swivel you would need to position the dma fairly accurately anyway. If you are working in the North Sea I would guess your vessels have a decent DP system (Class III?) so you should be able to be pretty accurate in deploying your kit.

Would be useful to know how it goes.

 

[roymack]

Ussuri

yes, we will be operating a dp3 vessel as its in norweigen waters. i will keep you upto date on eventually what we decide. it would be quite good to try the swivel base just to try a more advanced method other than the conventional method using the tirfor, but could be to costly for this specific project. thanks for the input.

Roy

 

[doig]

Roymack,

OK, I get the picture. In my view your group is the 'contractor,' tasked to both install the P/L & tie it in with spools. Is this correct? Is your group installing the P/L? The tie-in diving from the DSV?

Airbags should provdie the control you'll need.

What's the length of spool you're expecting, i.e, from the laydown target to the riser flange at each end? Straight? Z-spool? Is your group providing all materials (line pipe? T-L & swivel flanges?)and also surveying the spool gap and geometry? After the post-lay spool survey the fabricated spool should be fabricated to accurate to +/-5 to 10mm, is that about right?

Re the swivel-base winch: I don't believe you will get anything more from it that you will from a conventional swivel snatchblock. Both will align with the load and react around the swivel-winch axis or snatchblock tie-back. Come-alongs to chain between multiple anchor points (DMA to platform leg, etc) provide infinite load line alternatives.



best,

Ima-Nemisis Doig
(an old diver)